Method of condenser assembly



Oct. 24, 1950 G. JVBAIR METHOD oF coNDENsER ASSEMBLY Filed March 3, 1944 Patented oct. 24, 195o George J. Bair, Corning, N. Y., assignor to Corning Glass Works, Corning, N. Y., a corporation of New York n Application March 3, 1944, Serial No. 524,908

The present invention relates to condensers and more particularly to condensers embodying a dielectric of vitreous material such as glass or the like. Although it has heretofore been proposed, from time to-time, that vitreous material be eme ployed inthe manufactureof condensersso far as applicant is-aware up to,` the present time no vitreous dielectric condenser has beenrdeveloped r the various qualities of which arefcomparable with condensers Ausing high grade mica as the dielectric.

vThe prime object of the present invention vis a novel method of manufacturing ccndensers of the vitreous dielectric type.

A further object is a novely method of produce ing a condenser wherein the dielectric and metal-` lic members may be bonded together into one coherent mass.

Other objects and features of the invention willi present themselves in the course of the description which follows.

The preferred embodiment of the invention will now be described, reference being made from time to time to the accompanying drawing wherev Fig. 1 diagrammatically illustrates a heating and pressing apparatus by means of which cer" tain steps of the invention may be carried out, and alsoshows an assembled strip'of condensers embodying the invention being conveyed into the Y furnace;

Fig. 2v is a diagrammatic view illustrating suitable `arrangement fordriving conveying and pressing .rollers associated withthe furnace of Fig ,1; A' l n Fig. 3 is assemblyembodying the invention asprepared for passage through the furnace; i

`Fig. 4 -is an end elevationv of a strip'of` condensers embodying the invention; vand Fig. 5 is a perspective View illustrating the step of separating a strip'of condensers into individual condenser units. f

Referring now to Fig. 3, the assembly as prepared for passage through the conveyerfurnace of Fig.-1, comprises a strip of sheetgmetall IIjof dimensions appreciably greater than a strip of condenser assemblies to be assembled thereon.: Arranged on strip II is a chalked asbestospadv I2 upon which is vsuperimposed astrip of glass film I3, Individual condenser elements or sheets I4 of metal foil are then arranged in laterally spaced relation on strip I 3 with one edge of each sheet `I4 set inward from the edge of' strip I3 and with `the yoppositeedge of each ,sheet` pro-1 an exploded perspective view of an:

i 4 claims. (C1. r9- 79) jected well beyond the opposite4 edge of the strip, the latter edge of the sheet serving as `one `tab or terminal of a condenser assembly. A second A strip of glass lm I5 is then superimposed ony sheets I4 and vertically aligned with strip- |13. Thevnext layer ofr the assembly iscomposedof laterally spaced metal foil sheets I6. Each sheet:

I6 is like sheets I4 but projects over the opposite edge of strips I3 and I5 and serves astheother` tab or terminal of a condenser. A third strip of glass iilm I'I is thenyarranged over sheetsl I6 in vertical register'with strips I3 and I5.- The numberof alternate layers of metal foil and glass .strips employed is of course determined by the.` .y capacitance of `the condensers desired. For Athe purpose of simplicity, a condenser strip havingE but three layers of metal foil has been shown. 1

It is often desirable to slightly reduce the ca,-v4

pacity of a completed condenser to a predetermined standardized value.

grantedAugust 6, 1946, to enable this to be done the sheetsl of the final layer may be iiagged and each branch of a sheet made available for separation from the sheet, thus enabling the capacity of a condenser to be reduced in one, two or more increments. To provide the foregoing feature, narrowA strips I8 of mica are arranged on the glass strip I'I a small distance yinward from the edge overwhich the final layer of metal foil sheets are to project, and serve to prevent a narrow ycross-sectional area of the attached ends of `the flagged sections of the iinal layer of: foily 'i sheets I8 from later becoming bonded to-jthe glass strip I'I.U `Afterzplacement of sheetsISon; strip I1 a narrow kstrip 2li of vglass -ilm4 is far-f l ranged to cover those portions of sheets I9 prop-lr jecting tothe left l(Fig. 5) of mica strips I8.

The glass strip may `be severed transversely between the individual condenserunits inv any conventional-glass severing fashion. It isfpreferred, however, to employ the thermal shock severing method taught and claimed in alSmith application S. N. 524,897 led March 3, 1944, As

taught by Smith, Nichrome or similar Wires 2| are arranged on glass strip 20 transverse thereto Wherever it is desired to later sever the assembled strip.r As illustrated, the wires 2| are arranged outside rtheedges of the end condenser pile-ups to trim excess end portions of the glassstrips therefrom and are also arranged intermediate v adjoining pile-ups to separate them from one another. Wires 2| and the "underlying assembly are next covered with a chalked asbestos pad As taught andy claimed in a Smith application S. N. 524,896. filed concurrently herewith now Patent No. 2,405,529,

B 22, which is then covered with a pad 23 of coarsely Woven material such as glass or asbestos cloth or the like, and the whole covered by a sheet metal plate 24 and the assembly placed on those rollers 25 at the left end of the furnace assembly.

Rollers 25 and pressing rollers 26 and 2'l are all driven by a single motor 28 as required to advance material through the furnace at a uniform predetermined speed.

Specifically, the motor 28 is coupled to a gear reduction unit 35 which, by means of a chain 36, drives pressing roller supporting shaft 31 in a clockwise direction while the rollers 25 receive their drive from shaft 3l through chains 38 and 39. Pressing roller 26 is, on the other hand, driven in a counter-clockwise direction by interposition of a pair of gears 40 in a drive between shaft 3l and shaft 4| carrying pressing roller 26.

The pressing of the assembly is essential to produce an intimate void-free bond between the metal and dielectric layers. The pressure necessary to -accomplish this, of course, depends on the number of layers in the particular assembly being manufactured. The pressure applicable by rollers 25 and 2l has accordingly been made adjustable by the use of scale beam weightedv levers 5U exerting downward pressure on the upper pressing roller shaft 4|. The passing of the strip through a pair of pressing rollers has several advantages over a method which would involve simultaneous pressure at all points along the strip. For example, by using pressing rollers, the passage of the strips through thefurnace is continuous, Whereas simultaneous pressing would require the more complicated intermittent movement of the strips. Also, since the pressing rollers actr only on a small fractionA of the strip surface at a time, the force applied need be but a fraction of that required in simultaneous pressing and there is less tendency to fracture the glass films. Furthermore, the actualv results of pressing with rollers arey believed to be superior to those attainable by simultaneous pressing in that in progressive pressing air voids in the assembly are progressively squeezed out, whereas by simultaneous pressing there is grave danger of air pockets within the assembly being merely compressed. This is` especially true of air pockets which lie a substantial distance inward from the lateral edges of the strip.,

In some instances it may be -desirable to give the condenser assemblies greater mechanical strength. This may be accomplished by substituting relatively thick strips of glass for the outer strips I3 and 2Q. If the outer dielectric strips a're relatively thick, the method' of fabrication, if desired, may be altered somewhat. For example, the sandwiching of the assembly between pads and protective metal strips can be dispensed with if suitably padded pressing rollers are-.substituted for rollers 25 and 2l. The thickness of the outer sheets may be increased to the point where they provide a strong glass case for the finished condenser thus making it possible to dispense with the protecting casing commonly provided for mica condensers; and this glass case will have a much lower stray field loss than when a plastic or similar case is used.

The furnace proper' comprises a pre-heating section 30, a heating and pressing section 3|, andan annealing section 32. As diagrammatically illustrated', each of the sections 30, 3l, and 32' contains. a pairV of electric heating elements. The electric current supplied to the elements of the respective sections of the furnace is so adjusted that the temperature distribution maintained within section 3D is such that an assembled strip of condensers attains a uniform temperature near the softening temperature of its glass strips by the time it starts entering section 3| and reaches or slightly exceeds the softening temperature `iust before entering pressing rollers 25 and 2l. The temperature distribution of section 32 is so adjusted that the strip issues therefrom with the glass in a strain-free condition and at a temperature approaching room temperature.

The strip, after issuing from the furnace, is divided into individual condensers or into laterally spaced groups by including the pressed-in Nichrome wires 2| in an electric heating circuit as illustrated inFig. 5, whereupon the wires are heated and severance effected by thermal shock. As separation is effected, the Nichrome wire also breaks away from the glass and may be again used.

As will be appreciated, accuracy of placing the foil sheets in exact predetermined positions in the condenser pile-ups is essential if capacitors are to be held within a predetermined narrow capacity range. With this fact in view, plate may have score lines to indicate to the assembler the distance inward from the glass strips at which the foil sheets are to be placed. As a further precaution against shifting of the foil sheets and glass strips, the respective strips and sheets may be temporarily glued to one another. With metal plate arranged on a suitable heated hot plate, diphenyl may be used as the temporary adhesive, as it will be volatilized as the assembly passes through section 30 of the furnace. If desired, the mica strips I8 and Wires 2| may also be temporarily glued to the assembly to assure their remaining in place until they are bonded by heat and pressure to the assembly. The asbestos pads I2 and 22 and the cloth 23 provide a cushioning action which compensates for slight irregularities in the glass strips of the assembly while being subjected to the pressure of rollers 26 and 2l. bestos pads |2 and 22 prevents objectional sticking of the glass to the pads.

While the pressing of the assembly is taking place, the wires and metal foil are .wet by the softened glass and become thoroughly bonded thereto. Obviously, the glass strips of the assembly at the same time become bonded to one another wherever theyoverlap the foil sheets and in the areas between pile-ups. It will be appreciated therefore that the strip issuingl'from.

the furnace comprises a unitary body of glass having imbedded therein and thoroughly bonded thereto the metal parts of the assembly.

As will be appreciated, the transverse flagged sections of` sheets 9 arranged over the mica strips I8 do not bond to the mica. The condenser capacity, accordingly, can readily be reduced by removing one or more of the unbonded portions from a sheet I9.

What is claimed in the instant application is:

1. The method of manufacturing a condenser assembly which includes assembling a pile-up of alternate glass nlms and metal foil sheets, employing a volatile adhesive to temporarily hold the respective films and sheets in their assembled relation, subjecting the assembly to slight compression while moving it through an atmosphere so heated as to drive off the temporary adhesive, thereafter heating the glass to a softened condition, progressively subjecting theassembly to a The chalking of as relatively great compressive force suillcient to bond the lms and sheets to one another and slowly cooling the assembly to below the strain temperature of the glass.

2. The method of manufacturing condensers which includes assembling laterally spaced pileups of metal condenser plates in vertical spaced relation alternately with strips of glass, heating the assembly to the fusion temperature of the glass while subjecting it to a compressive force to bond the plates and glass to one another, slowly lowering the temperature of the assembliT to room temperature and separating the several pile-ups into separate condensers by severing the glass along lines between the respective pile-ups.

3. The method of condenser manufacture which includes piling sheets of metallic foil into laterally spaced stacks while vertically separating the sheets of the respective stacks with strips of glass, heating and pressing the whole into a dense coherent mass and separating the respective stacks from one another by fracture of the glass along lines running between stacks.

4. The method of manufacturing condensers comprising essentially alternate layers of glass and metal foil bonded to one another which comprises building up a pile of at least three strips of glass lm with a row of sheets of metal foil laterally spaced from one another between the upper and intermediate strips and a similar row of sheets of metal foil between the intermediate and lower strips, heating the assembly to the softening temperature of the glass, pressing the assembly while so heated to bond the whole into a dense mass, annealing the assembly and then separating the several laterally spaced piles of metal foil sheets from one another into individual condenser assemblies by fracture of the glass along lines intermediate thereto.

GEORGE J. BAIR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

